[PATCHv0 0/3] rtc: Abracon AB-RTCMC-32.768kHz-B5ZE-S3 I2C RTC chip support

[Arnaud Ebalard]

Hi Andrew,

This series adds support for Abracon AB-RTCMC-32.768kHz-B5ZE-S3 I2C RTC
chip. Unlike many RTC chips, it includes an internal oscillator which
spares room on the PCB. It also has some interesting features, like
battery low detection (which the driver in this series supports). The
only small "limitation" (mainly due to what RTC subsystem expects from
RTC chips) is the fact that its alarm is accurate to the second. This
series provides a solution (described below) for that limitation using
another mechanism of the chip.

I decided to split support between three different patches for
this v0:

- Patch 1/3: it simply references Abracon Corporation in vendor-prefixes
  documentation file. As Abracon has no NASDAQ ticker symbol; I have
  decided to use "abcn" (I initially started my work w/ "ab" but later
  changed for "abcn" which looked more meaningful)
- Patch 2/3: it adds initial support for the chip and provides the
  ability to read/write time and also read/write alarm. As the alarm
  the chip provides is accurate to the minute, the support provided
  by this patch also has this limitation (e.g. UIE mode is not
  supported).
- Patch 3/3: the chip supports a watchdog timer which can be used to
  extend the alarm mechanism in patch 2/3 in order to provide support
  for alarms under one minute (e.g. support UIE mode). In practice,
  the logic I implemented is to use the watchdog timer for alarms which
  are at most 4 minutes in the future and use the common alarm mechanism
  for alarms which are set to larger values. With that additional patch
  the device fully passes the rtctest.c program.

I decided to split the driver between two patches (2 and 3 of 3) in
order to ease review: patch 2 should be pretty straightforward to read
for someone familiar w/ RTC subsystem. Patch 3 only extends what is in
patch 2 regarding alarms. If you prefer a single patch in a v1, do not
hesitate to ask.

The set currently applies on top of 3.19-rc4 but I can rebase it against
something else if you prefer.

Cheers,

a+

Arnaud Ebalard (3):
  of: add vendor prefix for Abracon Corporation
  rtc: add support for Abracon AB-RTCMC-32.768kHz-B5ZE-S3 I2C RTC chip
  rtc: rtc-ab-b5ze-s3: Add sub-minute alarm support

 .../devicetree/bindings/i2c/trivial-devices.txt    |    1 +
 .../devicetree/bindings/vendor-prefixes.txt        |    1 +
 drivers/rtc/Kconfig                                |   11 +
 drivers/rtc/Makefile                               |    1 +
 drivers/rtc/rtc-ab-b5ze-s3.c                       | 1031 ++++++++++++++++++++
 5 files changed, 1045 insertions(+)
 create mode 100644 drivers/rtc/rtc-ab-b5ze-s3.c

-- 
2.1.1